Central timing deficits in subtypes of primary speech disorders.

Childhood apraxia of speech (CAS) is a proposed speech disorder subtype that interferes with motor planning and/or programming, affecting prosody in many cases. Pilot data (Peter & Stoel-Gammon, 2005) were consistent with the notion that deficits in timing accuracy in speech and music-related tasks may be associated with CAS. This study replicated and expanded earlier findings. Eleven children with speech disorders and age-and gender-matched controls participated in non-word imitation, clapped rhythm imitation, and paced repetitive tapping tasks. Results suggest a central timing deficit, expressed in both the oral and the limb modality, and observable in two different types of timing measures, overall rhythmic structures and small-scale durations. Associations among timing measures were strongest in the participants with speech disorders, who also showed lower timing accuracy than the controls in all measures. The number of observed CAS characteristics was associated with timing deficits.